I've always loved Mizani prods. but a stylist told me that Mizani is not what it used to be unlike 15 years ago. the company has been bought out, therefore the product quality has diminished.Never heard of Giovanni but I'll do a little research. On the other hand, I used Mizani's products once or twice and it's really good too.
If it works for you keep up with it! this is just some information, i thought i'd pass on, don't know how true.
however, she is not the first to say this, a few other stylists have mentioned this in the past.